Ask any question you want about Physics

originally posted by: greenreflections
You said that at least it contains some energy. Why 'some'? Would it be safe to say instead that deep space (space-time) is filled with
energy?

I'll be more specific than "some". If you live in an average home and use an average amount of energy, here is how much vacuum space it
would take to contain the amount of energy your home uses in one day:

you'd need to extract 100% of the vacuum energy from about 57.4 trillion olympic pool volumes per day to power the average home.

The thread
goes on to explain how we probably can't extract vacuum energy, but that gives you some idea of the energy density of the vacuum, based on dark energy
observations.

To put it another way, all the energy in a vacuum the size of an olympic sized swimming pool wouldn't be enough to heat a cup of coffee, even if you
could extract it, which you can't. So to me, that means the vacuum is not "filled with energy" though perhaps that's a subjective concept, which is
why I put some numbers to it to take out the subjectivity. 57.4 trillion olympic pool volumes isn't subjective; it contains the same amount of energy
the average residence in the US can buy from the electric utility for $3.12 (at the US average rate of $0.13/kwh), a days worth of electricity.

You said that at least it [vacuum] contains some energy. Why 'some'? Would it be safe to say instead that deep space (space-time) is filled with
energy?

If I say that a glass is filled with water, I mean that the glass is full to capacity and no more water will fit. I would be hesitant to say that
space is filled to capacity with energy.

However, you are correct in that there is energy everywhere and to find a parcel of space that does not contain energy is highly unlikely. In that
respect it might be defensible to say "filled", but to me it would feel weird.

I

Hi.

It would feel weird? Weird in terms that space is filled with energy entirely? I tell you more. IMO, energy is driving force expending space-time.
Unless you know of better source of space-time expansion.

You see, you allow the idea that energy is present somewhat in every cubic volume but ignore it's role as key player.

originally posted by: greenreflections
You said that at least it contains some energy. Why 'some'? Would it be safe to say instead that deep space (space-time) is filled with
energy?

I'll be more specific than "some". If you live in an average home and use an average amount of energy, here is how much vacuum space it
would take to contain the amount of energy your home uses in one day:

you'd need to extract 100% of the vacuum energy from about 57.4 trillion olympic pool volumes per day to power the average home.

The thread
goes on to explain how we probably can't extract vacuum energy, but that gives you some idea of the energy density of the vacuum, based on dark energy
observations.

To put it another way, all the energy in a vacuum the size of an olympic sized swimming pool wouldn't be enough to heat a cup of coffee, even if you
could extract it, which you can't. So to me, that means the vacuum is not "filled with energy" though perhaps that's a subjective concept, which is
why I put some numbers to it to take out the subjectivity. 57.4 trillion olympic pool volumes isn't subjective; it contains the same amount of energy
the average residence in the US can buy from the electric utility for $3.12 (at the US average rate of $0.13/kwh), a days worth of
electricity.

May be. But why you apply heat factor to swimming pool and why do you think it is not nearly enough to push cosmos expansion?
Do you have a figure that tells that cosmos might be driven to inflate due to still excess energy pressure since BB?

originally posted by: greenreflections
But why you apply heat factor to swimming pool and why do you think it is not nearly enough to push cosmos expansion?

When you asked about
vacuum being "filled with energy", I cited the swimming pool volumes because to me they show it's not "filled with energy" for my subjective
interpretation of that phrase, rather I'd say instead that the energy density seems quite low with $3 worth of energy per 57 trillion swimming pool
volumes of vacuum.

I didn't say it wasn't enough to accelerate the cosmic expansion, on the contrary, the observed acceleration of the cosmic expansion is the source of
those figures.

Do you have a figure that tells that cosmos might be driven to inflate due to still excess energy pressure since BB?

We don't really
understand "dark energy" well, but I wouldn't characterize it as "excess energy pressure since BB". It's just the observed amount of energy that's
required to cause the expansion of the universe to accelerate at the observed rate, which may be subject to some tweaking based on newer more accurate
observations.

originally posted by: greenreflections
But why you apply heat factor to swimming pool and why do you think it is not nearly enough to push cosmos expansion?

When you asked about
vacuum being "filled with energy", I cited the swimming pool volumes because to me they show it's not "filled with energy" for my subjective
interpretation of that phrase, rather I'd say instead that the energy density seems quite low with $3 worth of energy per 57 trillion swimming pool
volumes of vacuum.

I didn't say it wasn't enough to accelerate the cosmic expansion, on the contrary, the observed acceleration of the cosmic expansion is the source of
those figures.

Do you have a figure that tells that cosmos might be driven to inflate due to still excess energy pressure since BB?

We don't really
understand "dark energy" well, but I wouldn't characterize it as "excess energy pressure since BB". It's just the observed amount of energy that's
required to cause the expansion of the universe to accelerate at the observed rate, which may be subject to some tweaking based on newer more accurate
observations.

originally posted by: greenreflections
OK. How much energy per cubic foot of space-time is evident of significance to make space volume expand as a considered factor?

It's about
.000000000017 Joules per cubic foot.

originally posted by: greenreflections
Was there even a test proposal to confirm space-time expansion locally?

If someone proposed that, I would probably accuse them of having
absolutely no idea what they were doing, unless their proposal contained something that really surprised me. Instead I'll quote someone who
understands the situation, Dr. Carolin Crawford:

You have to remember, in astronomical terms, our solar system is absolutely tiny. The planets and the sun, and all the constituents of our solar
system, are very close together, and there’s no question that gravity wins in that circumstance.

Even on the scales of the galaxy, gravity is the dominating force. Even between groups or clusters of galaxies, gravity is gluing them together.
You're only going to get this expansion of space on the very largest scales, where you have sufficient space that the dark energy can
dominate.

I did see a scientist calculate what the effect would be on Earth's orbit and not only was the effect too small to measure, there were too many
confounding factors in the measurement that are much larger, such as the Earth gaining distance from the sun not because of cosmic expansion but
probably because of other factors such as the sun losing mass and transference of energy from the sun's rotation to Earth's orbit because of Earth
creating tiny tides on the sun like the moon does to Earth. For similar reasons the moon is moving away from Earth not because of cosmic expansion but
because of tidal interactions between earth and the moon.

Ah. I was not thinking of an empty parcel of vacuum of deep space. That is where my thoughts diverged from yours. I was thinking of a parcel of space.
When I add a stream of photons to that parcel, there is more energy in that parcel of space than without the photons. I can add almost arbitrary
amounts of photon streams; heck, I could add a spring that is compressed with clamps and there is more energy in that region of space. But turns out I
was not thinking of true vacuum.

originally posted by: Nochzwei
If you achieve anti gravity effect wrt time , it would imply gravity can be quantized, wouldn't it.
Read the thread in my signature.

I don't know what you mean by anti-gravity with respect to time?

There is bending of space-time in every lab though. Anyone can see and feel the effects of the Earth's gravity in any lab.
As you go out into space the gravity diminishes correctly according to theory.

originally posted by: Nochzwei
If you achieve anti gravity effect wrt time , it would imply gravity can be quantized, wouldn't it.
Read the thread in my signature.

I don't know what you mean by anti-gravity with respect to time?

There is bending of space-time in every lab though. Anyone can see and feel the effects of the Earth's gravity in any lab.
As you go out into space the gravity diminishes correctly according to theory.

I did and I could literally write a book about what's wrong with that experiment. I'm not going to write
an entire book and I already commeted on the candles in that thread, but I can elaborate on some of the problems with using the brightness of candles
as indicators of anything:

Given accurate enough measurements of a candle's brightness, even a single candle will not burn with constant brightness, but will vary in
brightness as it burns.

Given even a single candle doesn't have constant brightness, then it follows that two candles will also have at least some small difference in
brightness if the measurement is accurate enough.

There doesn't seem to be any controlled effort to measure the distance from the camera to the candles. Even if the candles were exactly the same
brightness (they aren't), the amount of light hitting the camera will vary approximately with the inverse-square of the distance.

Camera and human eyes both have a further source of error as they both have an iris that changes the size of the opening in each and determines
how much light enters versus how much is blocked. They use similar algorithms based on the total brightness of not only foreground objects like
candles but also of the background, which there seems to be no effort to control.

All the above would be serious issues for accuracy, even if using candles inside where they weren't exposed to wind as another variable. These
candles are outside and one is closer to the edge of the building where the building wall doesn't protect it as much from the breeze as the other
candle closer further from the corner and better protected by the wall.

The subjectivity of viewing the candle brightness could be reduced by using a light meter but even using a light meter would require careful
consideration for some of the above factors, for example the candles would all need to be against a similar (maybe dark) background, at the same
distance, with no breeze. Even then you would probably need to characterize the inherent statistical variability of the candles brightness and MAYBE
if you used 20 candles for the control and 20 candles for the hypothesis, you could make a statistically valid null hypothesis for how much measured
difference between the two groups would exceed a certain confidence level, such as three sigma.

Here is an example of a light meter though there are many styles available:

One reason you need a meter (we both need one) is that sujectively, without a meter, the claim made in the video for which candle is brighter appears
opposite to my perception, but I would defer to a calibrated meter as I don't claim to have any superhuman skills in detecting candle brightness
accurately.

All of the above observations are valid regardless of the purpose of assessing the brightness of the two candles, but let's address the purpose for a
moment. Am I correct in understanding that the candles' relative brightness is intended to infer some measure of the relative passage of time? And if
so, why wouldn't we try to measure the passage of time with, oh, I don't know, maybe something like clocks, instead of candles? Here's
one not much bigger than a coin which isn't quite as accurate as the NIST clocks but it's pretty good:

To measure small differences in the passage of time, NIST used more accurate optical clocks, so how accurate your clocks need to be depends on how
much difference in the passage of time you're talking about. The optical clocks could measure a difference just from raising or lowering the clock
about half a meter. The small chip clock isn't accurate enough to do that.

This is just the tip of the iceberg of experimental problems, so this experiment is not the one that will overthrow Einstein's theory of general
relativity.

like most other scientific experiments there is a limit to LIGO's sensitivity. essentially LIGO mark one had limited sensitivity to a very limited
frequency of gravity waves. LIGO 2 expands that window. LISA will too. There are new ideas about gravity wave sensors that will make future sensors
more sensitive. meanwhile astronomical instruments are reaching sensitivities that should be able to observe gravity wave effects around neutron
stars. it's not a shot in the dark WRT gravity waves either because Relativity predicts them and they are fully expected to exist.

in theory there is unlimited energy in the vacuum however it is not accessible in large amounts and this is a physical limitation and not a technology
or engineering problem. in terms of probability only the most miniscule amounts of ZPE states are even approachable by way of analogy if the ZPE were
an ocean only the sea mist reaches us with no real probability of even getting our toes wet.

this works to satisfy the physical constraints of the universe WRT thermodynamics and other such rules. sure there are instances of humongous energy
manifesting from the void (see big bang) but the odds are so long that thus far it has only happened once in the entire 14 billion plus year history
of the universe. the reason is for every such event there are unumberable events where the instance would be unnoticeable.

long story short borrowing large amounts of energy from the vacuum is prevented by unbridgeable gulfs of (im)probibility statisitics. it's not
technically impossible but it is mathematically infinitesimally unlikely.

Good post.
When you dilate time, it stretches the time vector and you can superimpose greater no of cycles on it, hence higher freq of light and expt repeated
several times with same result gives a measure beyond any reasonable doubt. so now you know what happens inside an orbiting atomic clock. So Einstein
is on extremely shaky grounds here mate.
a reply to: Arbitrageur

originally posted by: Nochzwei
Good post.
When you dilate time, it stretches the time vector and you can superimpose greater no of cycles on it, hence higher freq of light and expt repeated
several times with same result gives a measure beyond any reasonable doubt. so now you know what happens inside an orbiting atomic clock. So Einstein
is on extremely shaky grounds here mate.

Some clocks in orbit run slower compared to surface clocks, and some clocks in orbit run faster than
surface clocks, or at one specific altitude (where the net orbital time gain is zero), the orbital clocks and surface clocks can run at the same
speed.

That graph is based on predictions from Einstein's general theory of relativity and I've never seen any data contradicting it, perhaps with the
exception allegedly of the candles in the video you referred to, but I pointed out why candles don't make reliable clocks and they generally aren't
very good for precision measurements of time or anything else that I know of.

originally posted by: Nochzwei
Good post.
When you dilate time, it stretches the time vector and you can superimpose greater no of cycles on it, hence higher freq of light and expt repeated
several times with same result gives a measure beyond any reasonable doubt. so now you know what happens inside an orbiting atomic clock. So Einstein
is on extremely shaky grounds here mate.
a reply to: Arbitrageur

No this is just completely wrong. Time dialation occurs because velocity at which an object travels effects the space it has to travel through from
its perspective. And I'm not sure why you think Einstein is on shaky ground scientists have been trying to prove him wrong for a hundred years. No one
has found a way yet. There is little doubt velocity effects spacetime. And his equations works we prove it daily.

First in special relativity the effect occurs because the clocks in orbit are moving relative to the ground a Lorentz transformation occurs. This also
explains the graph arb posted. Why we need certain speeds to maintain cetain orbits. one more thing GR is a geometrical model describing the
translatory relation of mass and spacetime. It doesn't explain why it's so only that it is. So there is no doubt there is a relationship it's been
tested over and over. This is why any theory will incorporate Einsteins equations if it is to explain the universe. Because no theory can break with
the observed universe.

This content community relies on user-generated content from our member contributors. The opinions of our members are not those of site ownership who maintains strict editorial agnosticism and simply provides a collaborative venue for free expression.